Snowflakes are loose aggregates of ice crystals. 

雪花是冰晶的松散凝结。

No two snowflakes are ever identical. 

没有哪两片雪花是完全一样的。

Snowflakes were swirling in the air. 

天空飘洒着雪花。

Snowflakes are dancing in the air. 

雪花在空中飞舞。

The snowflakes were swirling about the streets . 

雪花在街道上涡旋。

Snowflakes were patting against the windowpane. 

雪花轻轻拍打着玻璃窗。

No sooner had I left the house than it began to snow.

我一离开家就开始下雪了。